Manufacture of antiknock gasoline



Aug. 3, 1943. c. K. vlLAND 2,325,892

MANUFACTURE OF ANTIKNOCK GASOLINE` Original Filed Oct. 23, 1939 2 Sheets-Sheet 1 CLA/ 25 KJ//L/q/vo V ATTORNEYl Aug. 3, 1943. c. K. vlLAND MANUFACTURE OF ANTIKNOCK GASOLINE 2 Sheets-Sheet 2 Original Filed OCt.\ 23, 1939 AND GASOL/NE /N VENTO? CLA/PE K. l//LA/va M gm' ATTog/VEK Patented Aug. 3, 1943 Y "2,325,892" MANUFACrUREoF ANTIKNojoK GAsoLiNE Y Clare Kenneth Viland, Martinez', Ca1if.,'assignor to Tide Water'Associated Oil Company, San

Francisco, Calif., a corporation of;Delaware A original applicatifnoctober zajissaserial No.. Y

300,727." Divided and this applicationiAugust 2,1940, Serial No. 350,038V f l Y l This invention relates to the manufacture of motor fuel by pyrolytic YconversionV of hydrocarbonsand is more particularly concerned kwith the production of light motor1 fuel of superior quality by a combination of cracking, distillation, and polymerization processes. Y f V 1t is theprincipal object of this'invention to provide a method jwhereby the antiknock prop erties of cracked; gasoline of desired vvolatility specications'may be substantially increased.,

It is also an object of this invention to increase the yield of the total gasoline fraction obtainable by a combination of the cracking and polymerization processes.` 1 y Itis a furtherobject of the invention to provide a method Awhereby a thermal polymerization process, operating in Yconjunction 'with a cracking process, maybe operated with greater freedom from the formation of polymer tars and coke resulting in longer periods of continuous operation without shutdowns for cleaning, repairs, etc. Other objects Will be apparent from the following description.

Y In the manufacture of gasoline motor fuel by the `so-called'cracking processes, wherein high boiling hydrocarbons are converted into lower boiling'hydrocarbons by the application of high temperatures', with or without pressure, there are formed large quantities of normallyr gaseous hy'T rocarbons including hydrogen, methane, ethane, propane, prop'ylene, butanes, and butylenes. `Most oithese have too high a vapor pressure 'to be included in marketable gasoline. However; the butanes and butylenes have sufliciently low vapor pressure-that a certain percentage may befincor- Y porated in the nished gasoline'without raising the vapor pressure ofthe nished product above the desired value. v l

As commonly practiced, in the manufacture of gasoline by cracking processes, the products resulting from the cracking operation are rst fractionated to obtain a raw pressure distillate of -the desired end lboil-ing pointpa gas oil fraction which is generallyrecycled to the cracking operation, and a residual fuel oil, The raw pressuredistillate is' thenk stabilized by fractional distillation to remove'the propaneand Vlower boil'- ing constituents as well as suiicientof the bu tanesand -butylenes to leave* a product' ofthe desired vapor pressure, such as for-` example 8 to l0 poundsfat'-100or F. ."ir1 alter na'te'methodv f of. stabilization 'commonlyemployed is'vto remove from the raw pressure distillate theentire amount of lighthydrocarbonsup to and including "the butanes'and butvlen'es. VFrom` these removed light hydrocarbons a ',fractionjconsisting of butanes and .butylenes "is separated.` A suicient quantity.; of this butanes-butvlenes fraction 'is then blended with heavier hydrocarbons of the pressure 'distillate to .bring the vaporA pressure oi the-latter up tothe desired value.V y Untilrecentlfy the normally gaseous,l hydrocarbonsv resulting from the stabilization'ofj the raw Y A pressure distillate have found use" only as reiinery fuel'or low priced gaseousI fuel.` yThe ex'- cess butaneebutylene has been marketed'inliquid y form under pressure as a cheap motor fuel. .Re-

cently it haszbecorne common practice'to convert a large portion of'these normally gaseous hydro'- carbons into hydrocarbons ofthe gasoline boiling range by means'of the so-called polymerization prog'zes'ses. Ascoinmonlyuemployed, these polymerization vprocesses consist briefly in subjecting the .fpropa'na` propylene, butanes j and butylenes to teinp'eratures'in therange of 1000 to 1300?. F. whereby an increase in the olenic content..

of theg'ases is obtained. The gasesare then subjec'tedioV temperatures of about 1000 to 115o F. at which' temperatures the olei-lnicmolecules tend tolrunite with vother olefines to'form higher boiling molecules most of which are inthe gasolineboiling rangeY However, substantial quantitiesofheavy oils are also formed which have va tendency toform'coke andjthereby interrupt the successful operation of the plant'.v vThe forniaftion of these heavy oilsv alsoresults in the degradation tolo'w pricedfueloil of constituents whicli vmight otherwise be manufactured into Ahigher priced motork fuel. By proper choice of constituents fed to lthe polymerization process', the

'formation o f these heavy oilscan be greatly .reduced Withja resulting higher `overallyielclrol the desired motor fuel.

.l'cco'rdingto the Vpresent invention a segreg'a tion ci the constituentslof vthe normallygaseous i hydrocarbonsis made in such a'vmanner that the portions blended with the stabilized prese' Sureuisnua to provide the desired vapor. pres'- sure arethose of the'high'est antiknock quality and at thesame timev the constituentscharged is'subjectedto such temperature conditions, with' or Without the aid of pressure or catalysts, as to convert a substantial portion of the oil into lower boiling hydrocarbons. vary between 800 F. and 1300 F., depending upon the reaction time and type of chargingV stock as is well known in the art. The products of the cracking operation enter fractionating zone 3 which may consist of one or vmore `fractionatingV Such temperature mayfrom Table 1 that a greater gain in octane numl `ber. for a given increase in vapor pressure is towers, Va series of stills, or any other suitablefractionating equipment. yIn the. fractionating zone the products are fractionated into a plurality of fractions represented as leaving the zone through lines 4, 5, 6, l, 8, 9,v I0, and` Il, in

their respective order of volatility. The lightest Vfraction composed of `hydrogen methane, and such other lightfractionsrwhich are unsuited for either blending into gasoline orfor polymerization. Ordinarilyf this fraction'willrinclude substantially all hydrocarbons which are more vola-v tile than propylene. This fractionrleaves the desired vapor pressure either by eliminating the lighter of the butanes-butylene fraction (i. e. isobutane) or by eliminating a proportional part of all the butanesbutylene fraction. This is clearly brought outV in the following Table `1 showing the octane ratings of the constituents of this'fraction:

TABLE 1 Vapor pressure Octane number Hydrocarbon F. pounds VA. S. T.

. 1 ,y per square inch D357-37T Iso-butanev v....-. 73 99 Butylenes 63 83 N.,butane 52 91 When itis realized'that the octane number of the total cracked gasoline is about 70, it is clear realized by the addition of either isobutane or normal butane to the cracked gasoline than by A the addition of butylene.

The propaneV-prop-ylene fraction in line 5 together with the butylene fraction in line 'l may be passedvto a polymerization plant, ywhich maybe of any type including the'use4 of catalysts if desirable. When using the thermal .polymerization Afractionating zone through line Y4 and'is used as Y fuel gas vor otherwise disposed of. The next Ylighter fractionleaves the `fractionating vzone through line 5 and consists essentially of propylene and propane which is well adapted as charging stock for the cracking furnace of a polymerization plant. The third fraction consists substantially of isobutane which leaves the fraci tionating-,zonerthrough line 6. According to the invention this .fraction is used as an important blending agent in the finished gasoline. It is therefore passed to storage in the gasoline storage tank ,20. The next heavier fraction consisting substantially offbutylenes leaves the fractionating zone through line .1. `According to the invention thisfraction is preferably used for charge to the polymerization plant in a special Way resulting in increased yields of polymer gasoline.l The fourth fraction, consisting substantially of normal butane, leaves the fractionating` zone through line 8, and is added to the finished gasoline/in gasoline storage tank 20. The fraction leavingY through line 3 is the main 'body of cracked gasoline and comprises theremaining components of the cracked products, which Yare desired in the nishedgasoline. Thisfraction is likewise passed; to the gasoline storage tank. A gas oil orrecycle fraction is withdrawnthrough ,lineV I0 and is introduced'with fresh 'charge entering the cracker through line I,'or if desired, kthis fraction may be wholly orinfpart disposed of in any suitable manner. The residuum from the rcracking is Vdischarged from the process through lineflrl.V l Y 7 v Y Itrmay' be seen that the gasolinemadeY by the process described above is composed of raw pressure distillate of the desired end'boiling. point which has been stabilized by the removal of Which'the cracked ygasoline is stabilized to the process, to which the invention is preferably di-v rected, it has been foundr that the yieldof poly'- mer gasoline obtained by subjecting butylenes to pyrolysis, or cracking, and polymerizing the productsisfar in excess Yof the yield obtainablefrom the same quantity of isobuta'ne orv butane'under the samel operating conditions; Thus, in elimihating the yliutylenes as blending stock for the cracked gasoline there is,` obtained a material which, while less suitable las a blendingvstock, is more desirable for use in the polymerization process. This is more clearly brought out in the following Table 2;which shows results` obtained in a conventional thermalpolymerization process when subjecting mixtures lof these hydrocarbons to pyrolysis and polymerization:

'v TABLE 2 Yields from pyjolysis and thermal polymerization Barrels poylmer Hydrocarbon gasoline per barrel liquefied gas charged Propane 0. 3 Y 0. 4

, l f 0. 5 Butylenes i 0. 6

While the propane-propylene fraction may be mixed with the butylenev fraction and the mixture charged to the pyrolytic coil of the polymerization process, or if desired, directly to the polymerization zone, the `invention comprehends a novel utilization of the two fractions whereby optimum operating conditions may be obtained from the polymerization process. This feature is shown in Figure 1. The propane-propylene fraction in lineA 5 is conducted into a cracking or pyrolytic coil I2 maintained at a temperature suflicientto Ysubstantially increase the olefnic content of the fraction. TemperaturesV of the order of 1000 F.'to 1300Y F. are satisfactory for this purpose. However, since the fraction consists mainly of propane and propylene, higher temperatures may be used than in the case where butanes and b utylenesk are present. Forthis purpose atemperature range of betweenr1125 and cluded in the nished gasoline. Y

l 2,325,392 71300 F. is preferred to obtainS optimum oienme content of the vapors andgases discharged from pyrolytic coil. The, gases issue .from pyrolytic coil .I 2 through-line I3. .At this point the butylenes in line 'I may. be introduced. The effector in-V troducing the butylenes at this point is to coolthe vapors-and gases issuing from coil `I2 to a temperature suitable for polymerization and simultaneously to heat the `butylenes to the polymerizay tion temperature which may be fromy1050 ,to 1150 F., a temperatureiof about 1100 F. being preferred. Thei mixture ofv vaporssand gases in line I3, being at the desired temperature, ispassed to polymerization zone I4 which may be in any desired form such as a coilor a chamber. VThe vapors and gases remainzin zone- I4 sufliciently long to produce a substantial quantity of hydroy carbons boiling Within the gasoline range orsocalled -Po1ymer gasoline. They then pass from zone I4, through linejl, into ractionating zone IB wherein they areV fractionatedto produce a polymer gasoline which passes. from the zone through line I9 to-tank 2li.Y The over polymerized It is obvious to those versed in fractional dise y tillation that absoluteseparation ofiso-butane,

butylenes, and normal butaneinto pure hydrocarbons is not generallycommerciallyv obtained,

charge, becausek the butylenesare "not l cracked therein.v n

Y(e) The temperature ofhthervaporsandrgasesfrom the pyrolytic stage ofthe rpolymerization process is reduced to the desired amount forpoly.- merization without the loss of heat.'

(j) Buty1ene;used as a quench material the l' pyrolized propane fractions is notsubjected to y undesirable pyrolysis, Vbut is charged directly to tionzonesas more fully :described belovvin the .preferred form of the invention maybe as much as 120% of Vthenorrnalyields indicated'in Table 2l Q (h) Conversion per pass 4through Vthe'e'quip the plant or reducing the size of equipment-frev quired for a given amount of product.

Figure 2 illustrates apparatussuitable forearrying Vout Aa preferred formV of the invention, it being understood that in both gures valves are to, be inserted at any and all, parts Vof the'sys- I tem for maintaining Va desired or necessary pres- Y sure, or flovv. Gasand-.cracked gasoline from'an.

oil cracking process'enters gas separator'f22 through line 2| Gas is removed froml the sep# and that the fractions inlines 6,.,1, and 8V will not generally be pure isobutane, purebutylenes,;and pure normal butane respectively.l Absolute `fracn tionation is not essential tothe-successiu1` operation of therprocessr.; The inventiondcomprehends j It is also obvious that, if desired, the operation*Y of fractionating zone 3 maybe so conducted that` the products obtained inV streams and S may be,

obtained ina single stream. Thus, the normal butane and the heavier components of the cracked gasoline may be rfractionated in a single stream vvithout departing from the spirit of theinvention.

It will be apparent that .at times the Vvapor pressure desired .inthe finished gasoline may be somewhat below that obtainable VWhen blending theentire amounts of vthe isobutane and normal butane fractions.` i Under -such conditions less invention,A however, contemplates v`that atleast r15% of` the total .isobutane yand normal butane `present in the products of crackingshall be in- The advantages of the -ventire system may be summarized as followsr" Y (a) The'nnished gasoline is brought up to the desired vapor pressure by blendingr constituents which are ci highest octane rating andwhichare least suitable for polymerization.

(b) Material 'which is least suitable for blend- Y 21 intogstill-SD, Where the `propylene and 'heavier arator .22 through line 23'and enters absorber 24 Where it is stripped of substantially'allpropyle ene and heavier hydrocarbonsY and the stripped or xed gas consisting essentially ofethaneiand lighter 'hydrocarbons is Withdrawn fromthe systemby `line 25..` Absorption oilA Yenters the absorber byline 26 through heatv exchanger21 and coolerv28 and'rich oil leaves the absorbenby..`v`

constituents contained Yinthe 'cracked' gas V*are distilledoverhead into' line 3I. and ..in'jectedinto stabilizing column 32, Yinto which isfalso charged the unstable gasoline from separatorZZ by means of line 33. Stabilizer 32 is operated at'such pressure and temperature conditions that the over-v ,50 head distillate in' line v34 V-consists essentially of ing purposes is charged to the polymerization merizationprocess resulting in higher yields of olenic vapors and gases from the propane propylene, propane,`r and iso-butano hydrocarjbons which are passed into tower for further fractionation removing overhead va propylenepropane fraction through line 36which is vlioluee' amounts of thesefraetiong should be used. YThe iied lneoolerJSfI and passed into tankA 38.1 Anyy uncondensed 'vapors are Vvented from vtank 38 through line 39 and reprocessed ingabsorberv24. Llqueed propylene-propane Vvin tankV 38 `is v from Athe stabilizing column` :t2-Which` product'V contains substantially al1 the butylenesan'd,heav- 1 ier hydrocarbons i'seharged through line Yl2 into Y fractionating columnr43; Column 43 is operated at such-pressure and temperature conditions'that the'gasoline is stripped of .substantially all vbu Y, tylenes ,andthestripped gasoline, consisting of.- f substantiallyy all normal butane and heavier hy- `drocarbons, leaves the column through cooler .d4

K and line 45 ,vandisepassed intogasolineproduct vreceiving tank 46.

The overhead product from tower-43, consisting of a butylene fraction, is re'-r moved by line 41 andgcondensedfinr coolerrlIB pors are vented from tank 49 through linezil 'andlreprocessedin absorber 24;` The liqueed butyleneifractionisLpumped*by means of pump 51 into the-stream of fpyrolized fractions f in` line 52 from furnace-JH". The butylene fraction enteringLline`-52-may or may notbe heated in heater 53 beforeg commingling with i the "pyrolizeid fracttomoepending. upon quantity4 and temperature or-the;butylenefraction, but in any 'case enters line" atl temperatures substantially .below cracking.' or-r polymerizirurr temperatures. temperature ofthe pyrolized fractions leaving furnace- 4 I f is so adjustedV thatV the'iinal temperature" at the inlettoreaction zone-54. after.v admixture of.' the butylene fractioninline 52 `is at theo desired polymerization. temperature without thofurther-'addition of heat. l

Generally it. has` been found desirable from the: standpoint ofr. obtaining optimum polymer gasolineyields lin a conventional thermal polymerization: plant to:l adjust the temperature of pyrolized vapors-.and gases-leaving the pyrolysis cluding.unconvertedLrecycle fractions When' cornparedwith thenetifresh*liquefied'gas charge obtained from the oil cracking process through linel Y '2d-is in thefratio of. between about 5 to 1 and 9 to 1f. They maintainingV of' such; furnace` recycle `ratios is an important factorin'prev'enting excessive formation ofi incondensiblegas,v coke, and

tars tothe detriment of gasoline yields and length downtandcleanedout; n 'i .Undenconditions of the prefe'rredaforrn of the of' runs obtainable-before the'pla'nt must be shut Thebottoinfproduct from tower .5B containing the Y polymer gasoline, tar and .the'remain'der ofthe C4 and lighter:hydrocarbons:is-cooled in cooler 58V andla `portion returned Iby means .of :line 59 back into-line 55 as-a'quenching medium to stop thereaction obtained 'in Izone 54. -The remainder is' passed Vthrough linelliinto tower Bl where all C4 andrlighter. hydrocarbons are.r removed `overlsubstantially'all theisobutane is cooled in cooler inventionv it is: now possible to increase the-con- Y version: peiypassdn the. cracking vorfp'yro'lysisuzo'ne preceding the=po1ymerization stepV by increasing quenching; with the butylenes fraction before subtank 64 are vented'byline 65 back into absorber 24 'for reprocessingand the: condensate 4removed byline Gif consisting largely of propylene and propane, may be injected -by lpuxnpll through line 68 back to pyrol'ysi's vfurnace 4I or,A if operating'conditi'onsare suchv that the condensate in line 66 contains substantialfamounts of butan'es and-butylenes, theicondensate islpassed through line BS'fback into line 2l and separator 22 for reprocessing in the gas-fractionatingsystem. The bottom product 'from tower `6| comprising the stableV polymer gasoline'` and p'olymertars is passed! through-line linto fractionating tower ll where vpolymer'gasoline is removed overheadv throughl cooler- 'l2-"and line 13 into fgasoline product tank 46.1 Polymerftars--leaving tower'll are cooled'. in` coolerV 'Il and VVpassedthrough line l5-into tar product;receiving-tank'll. Y

' Returning lto tower 35`-in which was-'processed the propylene-propane-isobutane fraction previously mentioned, v'the bottom product comprising l'i'- an'd'passed-by means of line'18intogasolie product Vtank 16'=1whichthenfcontains the (a) normal butane Vand all heavier gasoline products from'itne cracking operation r'stfmentioned together with any normal `vbutaneV product by therconversion temperatures by" 5 to25 VF. when' polymerization z'one vexpressedas liquid volume of totalr chargeincludingv recycle Vfractior'is dirived: from` the oilcracking.` process may be reducedptojbetween 4to l and'f to 1 thereby increasingA throughput considera-bly While also ob- Y vided by the liquidlvolume of the fresh` feed detaining greater gasoline yields. In other words,Y

dueto'the'novel process herein not only isthereV less stock.available-for` recycling due tofgreater Y conversion into valuable' gasoline fractions but there isless' recycle` stock used Whichmaterially sired; anda temperature of about 1050 to 11.50

- 'lwithink the reaction `or polymerizationjzone is preferred; The liquid'pol'ymers and gaseous fractions leaving zone 54Y are treated by well-known methods for separation of liquid polymers and Y for recovery and'recycling to furnace lll,Y or reaction -zone 54, the normally gaseous liqueable hydrocarbons which wereunconvertedA in the process;

mal polymerization of propylene, propane or VVbutylenesjY `(b) the polymer gasoline? product obtainedbyj-thermal p'olymeiizz'rtion of propylene, propanegfand butylenes; and (c) the isobutane fraction contained in theoriginal crackedlga's and gasoline together with! any isobutane produced bytherm'a'l polymerization 'of propylene, propane', or butylenes. a

"Ifhe advantages to be-gained'bythe invention fromY the combined operation `of f a crackingand Vpolyrnerizationi V plantto 'produce -a finished gaso.. f line'oi' suitable'va'por pressurasuchfas 9# Reid' vapor pressure, is clearlyshownl by the example given in Table' 3,' wherein Yt'he'totalyield and i octane number of Astabilized gasoline: obtainable from a typicalunstabiliz'ed, cracked gasoline-when operating under optimum?v conditions: in conventional methods iscomp'ared'to the total yields and octane number Vobtainable from''the'preferred form of the invention as outlined above'in'the description of Figure?. It' will .benoted that, forevery 1 000 barrels-of` crackedproducts available for the productionlofhnished crackedv and polymer gasoline operationunderlthe invention results in an;increasedyield of 22vbarrels of finished gasoline having an enhancedV octane rating of 0.5 octane number'ove'r that obtainable This Ymay be furtherexernplied by passing 'Y such. reaction products from zone 54 through lineinto fractionatingf tower 56 whichv isY operated at' such temperatures and-pressures that underV goodpractice-with conventional operation. Y This increased'Y yield 'andoctane number obtainable according'to the invention. is equivalent to the addition of'22'1barrels of 92.7 octane Y. tion of tar and coke.

In the example shown in Table 3 the operating conditions of. the various units were chosen so as to give optimum yieldswith minimum produc- Such conditions arey shown in Table 4. Y

' TABLE 4 I Char e Cgggil Pffefed g operatio operation Total fresh liquefiable gas charge. to Y* process A barrels.. 1, 000 1,000 Total 'furnace throughput do. 6, 500 4, 750 Total fraction added to polymerization zone (containing 75% butylenes barrels- 0` 250 Total throughput ratio 5. 5:1 5:1

Conven- Preferred Yleld optgltn operation Y Polymer gasoline barrels.. 415 455 Polymer tars do 35 30 Residue gases MCF.. 1, 400 1, 240

Conven- Preferred Operating conditions optrriflm Operation Temperature pyrolysis furnace out F l 130 Y 1, 150 Temperature reaction zone out; F l; 085 l, 025 Temperature butylenes to reaction zone F vo5() Pressure furnace out. unds 500 500 Pressure reaction zone ou do 480 480 When the typical cracked distillate shown in liquid mixture suitable for Table 3 is stabilized according to the present invention, with the elimination of the butylenes and the retention of the iso-butane and normal butane, a stabilized cracked gasoline results which has the following composition:

Per cent by Volume Due to the'variations in composition of cracked distillates and accuracy of renery fractionation Tann-E "3 Wichcmiveiitional;stabilizing1 im i ,i Y f U 1 proved operation o1 stabil- Constituents Pnt clafftigg ttrq, fiziiig .and-i'ilieigirial :polynieri.V i"

present in n o o] mmation lam;Y 'zationplants .for producing Y totall`unta= to mg# gasoline p 9#-gasolineas-flcscribed #M i' h'ize t' ".L 1f L;

cracked gas amga'sollme' Barrels Barrels Total Barrels i Barrels Totai' afl-re s Vpolymer cracked barrels polymer cracked barrels v gasoline gasoline gasoline gasoline gasoline gasoline Prop'y1ene 2s 14 Y 14 g 17 i7 Propane.-- 86 26 26 31 3l ISobutane.-- 16 3 11 V16 16 Butylenes 52 16 26 42 Y 37 37 N. binarie 46 9 .23 g 32 j46 46 Iso-pentane and heavier 772 772 K 772 772 772 Tomi 1,000 'es 829 se? ss 834 91e Vapor pressure 100 F pounds Y 9 Octane No. (A. S. T. M. method D-357-37T) 71. 8 72. 3 Increased yield per 1000 barrels cracked products; producing saine vapor pressure gasoline 22 Increased octane number of total gasoline of same vapor pressure.. 0.5 Equivalent blending octane number ol' the 22 barrels increased production if mixed with conventional production 917.7

the composition of cracked gasoline stabilized according" tothe invention will normally fall within the following limits:

Butylenesf. 0-` 1.5 N. Butane 4.0- 7.0 .Iso-pentaneand`heavier 90.095.0

.` M i' l Pounds Reid vapor pressure@ 100 F 7-10 While the invention is `primarily directed tok the manufacturelofgasoline within specification limits customarily employed Vin carbureted automotive engines andsuch is the preferred embodiment, the'inventionis not restricted to such and the term gasoline used inthe appended claim should'b'e construed to include any normally y ,use as-a fuel for internal combustion engines of the carbureted type.` The terms propane-propylene fraction, isobutane fraction, butylenes fraction, and normal butane fraction are used to indicate fractions predominating in therespective hydrocarbons named and containing at least '75% ofthe respective hydrocarbonsv available inY the stock Vsubjected to fractionation.

It is thus seen that the herein described operations kcomprise tW'o methods of producing a nished gasoline of overlapping boiling ranges either of which provide a. motor fuel of increased octane number and the products of which, when blended as in arcontinuous refinery operation, not only provide a finished gasoline of increased octane number, but also a greatly increased yield of such gasoline having `a required vapor pressure.

This application is adivision of my copending applicationV Serial Number 300,727, led October I claim as my invention:

` In a Vprocess of making nishedgasoline'of desired Vapor pressure from the products .obtainedV from cracking relatively heavy hydrocarbons thus producing unstabilized gasoline, the

step which comprises: fractionating an unstabilized cracked gasoline intoa propane-propylene fraction, an iso-butane fraction, a butylene fraction, and a heavier gasoline fraction; heating the propane-propylene fraction to between 1125 F. and 1300 F. to increase the olefine content, mixing said butylene fraction With thethus-treated propane-propylene fraction andpassing the mix` Per cent by Volume ture through a thermal polymerization zone above tion arefblenled without furtherV treatment and 1050 F. and below the cracking temperature of the butylene fraction used as a quench material the butylene fraction, stabilizing the-thus-'formed" "for the pyrolized Ypropane-propylene fraction is' polymer gasoline and finally lblending same with not1 subjectedA to undesirable pyrolysis but is said iso-butane fraction and said heavier frac- Charged directly intoV the polymerzatiOn 20H8, tion to form a finished gasoline whereby the iso`v Y 1311115k nfileaflg the yldf gasolinebutne fraction and the heaver-igas01ineirac: 11 CLARELKENNETHMLAND 

